It is known that the water content of hydrogen peroxide solutions is disturbing in many reactions, e.g., in oxidations or epoxidations, see, e.g., Organic Reactions Vol. 7 page 395 (1953).
Thus, there were early attempts to employ corresponding organic solutions in place of pure aqueous solutions.
However in the production of these types of solutions there are difficulties.
Generally, to obtain organic hydrogen peroxide solutions, there are employed aqueous solutions of hydrogen peroxide as the starting material. These are either only diluted with the desired organic compound and subsequently the water removed by distillation or the aqueous solutions are extracted with the organic compound and if desired the water removed.
In both cases there are indeed obtained organic solutions of hydrogen peroxide whose water content, however, always is approximately 1 weight % or more, see, e.g., German Pat. No. 2038319 and German Pat. No. 2038320 as well as Kabisch U.S. Pat. No. 3,743,706 and British Pat. No. 931,119. The entire disclosures of the aforementioned German patents, Kabisch U.S. Pat., and the British patent are hereby incorporated by reference and relied upon.
Thereby, according to the process of German Pat. Nos. 2038319 and 2038320, there have been attempts to remove the water present in the organic solutions by distillation at reduced pressure or by azeotropic distillation with an additional entraining agent.
In the process of Kabisch U.S. Pat. No. 3,743,706, the extraction agent itself can be used as entraining agent for an azeotropic distillation. However, more precise details are missing.
Also in British Pat. No. 931,119 there is employed a component of the mixture for azeotropic distillation of water. However, in the production of organic hydrogen peroxide solutions from aqueous solutions besides the frequent too high content of water there is manifest a further, more substantial disadvantage.
During the removal of water at the pressures employed, a certain percentage of hydrogen peroxide is entrained with the distillate which leads to substantial losses of hydrogen peroxide. In repeating two of these procedures, the losses were between 0.5 and 0.6 weight %.
Besides, there occur further losses through decomposition in the sump.
In the process of German Pat. Nos. 2,038,319 and 2,038,320, there are employed organic phosphorus compounds or heterocyclic nitrogen compounds, in the process of British Pat. No. 931,119 and Kabisch U.S. Pat. No. 3,743,706 aliphatic or cycloaliphatic esters.
While in Kabisch U.S. Pat. No. 3,743,706 there is present no data in regard to carrying out an azeotropic distillation, in the processes of the other three patents mentioned, the operation is carried out at pressures far below 100 mbar, see the examples.
Although both German patents specify a general pressure range below 400 mbar, repeating the proceedure using triethyl phosphate or N-methyl pyrrolidone at pressures of 400 and 100 mbar resulted in hydrogen peroxide concentrations of 0.28 or 0.6 weight % and 0.26 or 0.8 weight %, respectively, in the distillate.
Besides, there occurs an additional loss of hydrogen peroxide of 7.5 or 4.1 weight % and 4.7 or 3.9 weight % based on the hydrogen peroxide employed. If there is calculated the loss of hydrogen peroxide through the amount of the distillate and the decomposition thus at a distillation of 400 or 100 mbar, the total loss is at least 7-8 weight % of the hydrogen peroxide employed. However, if one distills at substantially lower pressure, i.e., far below 100 mbar, then there are found still higher amounts of hydrogen peroxide in the distillate which amounts can be as much as over one weight percent based on the distillate; however, the examples were carried out at these pressures which were considered as preferred, see loc. cit.
Also, in the use of aliphatic esters as solvents for hydrogen peroxide, the azeotropic removal of water is carried out at pressures which are far below 100 mbar, see British Pat. No. 931,119 Example 1.
Upon repeating the preparation of a solution of hydrogen peroxide in n-propyl acetate and the azeotropic removal of water from this solution, it has turned out that the distillate contains more than 0.5 weight % of hydrogen peroxide at a pressure of 65 mm.
Therefore, according to the state of the art, there must be formed the impression that in a distillative drying of organic hydrogen peroxide solutions which is to be carried out at a reduced pressure necessarily, as a consequence, there must be considerable losses of hydrogen peroxide in large scale carrying out of the process.
However, not only the loss of hydrogen peroxide represents a considerable disadvantage of the previously known process, additionally the distillation residues were not free from water.
Thus, the organophosphorus solutions have e.g., residual water contents which are between 0.97 to 9.5 weight %. However, these types of solutions cannot be employed for oxidation or epoxidation.
Also, in the single example in German Pat. No. 2038320, the water content in the organic phase was 11.4 weight %.
Thus, a task of the process of the present invention is to produce a solution of hydrogen peroxide in an organic solvent in which there is no mentionable loss of hydrogen peroxide employed and which solution has a water content below 0.5 weight %.